crypto: shash - remove crypto_shash_alignmask

crypto_shash_alignmask() no longer has any callers, and it always
returns 0 now that the shash algorithm type no longer supports nonzero
alignmasks.  Therefore, remove it.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>